Figure shows an experimental arrangement for producing and observing Newton’s rings. A monochromatic source of light is kept at the focus of a condensing lens. The parallel beam of light emerging from lens falls on the glass plate kept at 450. The glass plate reflects a part of the incident light vertically downwards, normally on the thin air film, enclosed by the plano convex lens and plane glass plate.

The reflected beam from the air film is viewed with a microscope. Alternate bright and dark circular rings with dark spot as centre is seen.